Distribution and life strategy of the deep-sea crab Paromola cuvieri (Risso, 1816) (Brachyura, Homolidae) in the central Mediterranean Sea over twenty-five years

Abstract

The present study represents a new contribution to the knowledge on the distribution and life strategy of P. cuvieri in the central Mediterranean. During 71 experimental bottom trawl surveys carried out in the Northern Ionian Sea from October 1994 to July 2019 a total of 457 specimens was sampled from 91 to 1118 m in depth. The highest frequency of occurrence and density was observed in the 600–800 m depth range. The relationship between carapace length and depth was statistically significant showing a significant decrease in size with depth. The length-frequency distribution was unimodal for both sexes and there was a low number of small individuals. The most represented size classes for both sexes were between 50 and 130 mm Carapace Length (CL), with males significantly larger than females. The sex ratio by size showed an increase of males with increasing length. Of the sampled females, 50 were in ovigerous condition and 92 females were non ovigerous. P. cuvieri appears to have continuous reproduction throughout the year, with ovigerous females observed in all seasons, with the highest abundance in spring and winter and between 400 and 800 m of depth. The fecundity ranged between 138165 and 374453 eggs with a mean value of 217237 eggs. The eggs show a spherical shape and their mean size increased with maturity stage. Egg development appears to not be completely synchronous, and two patterns can be observed simultaneously. The relationships between CL/brood size and weight/brood size were highly significant. The relationships between width and hand-length of both chelae and Carapace Width (CW) for both sexes were highly significant. Time-series data showed a scanty abundance of P. cuvieri in the studied area with no trend over the period 1995–2019 with no significant trend over. Its preferential distribution on the middle slope was confirmed. Time-series data (1995-2019) showed a scanty abundance of P. cuvieri in the studied area with no signficant trend. Its preferential distribution on the middle slope was confirmed.